1. Field of the Invention
This invention relates to processes for the preparation of bisphenols and is more particularly concerned with an improved process for the preparation of Bisphenol A by the condensation of phenol and acetone.
2. Description of the Prior Art
The condensation of phenol with acetone to produce Bisphenol A [2,2-di(p-hydroxyphenyl)propane] is a reaction well-known in the art. A variety of catalysts has been suggested for use in this reaction. Such catalysts include hydrogen chloride (see, for example, U.S. Pat. Nos. 2,182,308 and 2,191,831), boron trifluoride (Chemical Abstracts 58, 3338c), perchloric acid (Chemical Abstracts 60, 1626h), benzenesulfonic acid (Chemical Abstracts 59, 511h), and various cation exchange resins (see, for example, British Pat. Nos. 842,209; 849,965 and 883,391). The use of various thiol compounds, in combination with one or other of the above catalysts, has been reported. Illustratively, U.S. Pat. No. 2,468,982 shows the use of thioglycolic and 3-mercaptopropionic acids and esters thereof as catalysts and U.S. Pat. No. 2,623,908 shows the use of combinations of such mercaptoalkanoic acids and hydrochloric acid. The use of thiophenols (U.S. Pat. No. 2,359,242), combinations of hydrochloric acid and alkylmercaptans (U.S. Pat. No. 2,775,620) and hydrogen sulfide (Chemical Abstracts 58, 1403e) has also been reported.
We have now found that the use of certain phenols and ethers thereof as promoters, in combination with known catalyst systems for the condensation of phenol and acetone, gives rise to significant improvements in the overall results achieved in said condensation.